Wednesday, November 2

Friday, November 4

Monday, November 7

Wednesday, November 9

Friday, November 11 - Remembrance Day

Monday, November 14

Wednesday, November 16

Friday, November 18

Monday, November 21

Wednesday, November 23

Friday, November 25

Monday, November 28

Wednesday, November 30

Wednesday, November 2

For 9.3 Lattice Energy of Ionic Compounds, concepts are important here: not numbers. Know about lattice energies being positive, and be able to compare lattices based on the charges and sizes of the ions involved.

Lattice Energy (E) = k __Q _{1}Q_{2}__

r

Now that we have a firm grasp
on the skill of drawing Lewis Diagrams, we can proceed onwards.

Lewis diagrams tell us about
the valence electrons in a molecule, and about the connectivity.

The Valence Shell Electron Pair Repulsion Model will allow us to predict the shapes of many molecules. 10.1 Molecular Geometry

The word Pair
is rather misleading in the VSEPR model.
I refer to "electron Groups"
(or E.G.) to
make it absolutely clear in deriving the molecular shape. An E.G.
can
be a single bond, a double bond, a triple bond, or a lone pair.

After a little demo with people and ropes - we tried the first simplest case of 2 E.G. using my steps.

Then, a real demo about silane!

Onto 3 E.G. and 4 E. G. and considering lone pairs on central atoms!

SKILL: You should be able to draw all of the basic shapes mentioned in class

Remember! This is an extremely important SKILL

Monday, November 7

I finished the rest of the shapes you will need to know.

Exercises from Chang: 7, 10, 12, 14 (except CdCl

You got back your tests - make sure you look at the breakdown on D2L!

Wednesday, November 9

10.2 Dipole Moments

Polar bonds can be examined to determine molecular polarity. Add up the dipoles, like vectors

Some molecules have polar bonds, but do not have an overall dipole moment.

Now we can relate the new skill of VSEPR back to the dipole moment of a molecule.

SKILL: Since we now know how to determine the shape of a molecule, we can figure out its dipole moment.

Clickers for VSEPR. Click here for the document.

Friday, November 11

No class

Monday, November 14

The next goal in lectures: relate our understanding of atomic structure to our understanding of molecular structure.

- WHAT: 2 models of bonding in molecules
- WHERE are the electrons? M.O. Theory - delocalised; Valence Bond Theory - localised directly between the atoms
- WHEN does bonding happen? if atoms have orbitals with similar energy and compatible shape (symmetry)
- WHY do we care? atomic structure allowed us to understand periodic trends, and why certain atoms combine in different types of bonds; molecular structure will allow us to understand reactivity between molecules!
- HOW does bonding happen? overlaps between orbitals (the bond is more energetically favourable than the energies of the individual atoms) - for M.O. model, we will overlap wavefunctions, more about VB model later...

Clickers for Bond Orders. Click here for the document.

Wednesday, November 16

More MO theory...

Important guidelines:

1. overlap must happen
- atoms need to be close enough

2. orbitals must have
similar energies

3. orbitals must have
similar/compatible
symmetry

We can use the M.O. model for
any molecule, but for this course we will only look at simple homonuclear
diatomics. We drew the M.O. diagram for oxygen. Click here
for the M.O. energy level diagram for O_{2.} Electrons are added
according to the rules we already know for atomic energy level diagrams.

Drawing orbital overlaps for p orbitals...

...some more bond order
calculations including O_{2}^{-} and F_{2} for homework!

Friday, November 18

Clickers for MO theory. Click here for the document.

Remember a pi bond is not as strong as a sigma bond - this affects the reactivity!...more later on this

The M.O. diagram tells us information about a compound's reactivity: Highest Occupied Molecular Orbital reacts with electrophiles, Lowest Unoccupied Molecular Orbital reacts with nucleophiles.

Exercises: 46, 47, 48, 52, 58

Now onto a DIFFERENT model: 10.3 Valence Bond Theory

The atomic orbitals we learned earlier will not give us the geometries that we predict from VSEPR! How do we rationalize this? We use the idea of

We made several types of hybrids before the demo...

Monday, November 21

Clickers for hybrids. Click here for the document.

Methane and Ammonia Examples: 4 sp

BF

Definition: single bond - sigma bond - located directly between the atoms

One more example of 3 sp

Definition: pi bond - located above and below the plane of the atoms

Double bond is sigma + pi = 4 electrons total (2 sticks)

Answers to homework: click here.

Wednesday, November 23

Clickers for hybrids. Click here for the document.

Triple bond - sigma + 2 pi = 6 electrons total (3 sticks)

The last two types of hybridisation we will consider:

5 sp

6 sp

Remember, hybridisation is a

We learned about the sigma-framework of molecules that have resonance structures, and that they have

An introduction to Line Drawings - look to D2L.

Exercises: 26, 34, 36, 38, 40, 42, 44 and 63, 72, 76 (except e), 80 (expect CdBr

Answers to homework: click here.

Friday, November 25

Clickers for hybrids and line drawings. Click here for the document.

Kinetics!

How
fast can a reaction go?

Speed
will depend on:

- The reaction itself
- The states of reagents
- The amounts of reagents
- The temperature
- The presence of a catalyst (more later)

13.1
The Rate of a Reaction: Rate is another word for speed - how a quantity (concentration)
changes as time passes.

The
rate of a reaction can be represented mathematically - 13.2 The Rate Law

For the generic reaction: Rate = k[A]^{x}[B]^{y}

For the generic reaction: Rate = k[A]

x
is the order with respect to A and is not related to a

y
is the order with respect to B and is not related to b

k
is called the rate **constant**:
for a given reaction at a given temperature.

x,
y, & k come from experiment, so we need to leave them as algebra until
we know some experimental details
Monday, November 28

Homework - Average rates example - for answers, click here

Determining the Form of the Rate Law requires the Method of Initial Rates.

SKILL:
My steps overhead allowed us to work through two examples. (See link on my main page for kinetics notes and these steps).

Homework for Initial Rates - for answers, click here

Remember that you can work out the units of k if you know the overall order.

Remember that you can work out the units of k if you know the overall order.

The
rate law used so far is also known as the differential rate law since it
involves a derivative.

The Integrated Rate Law allows the rate law to be converted to an equation where concentration depends on time. This is a much simpler experimental issue.

This is a good time to remember
about logarithms. See Appendix in your text!The Integrated Rate Law allows the rate law to be converted to an equation where concentration depends on time. This is a much simpler experimental issue.

Exercises: 2, 8, 16, 18

What if a reaction has more than one reactant?

More complicated math: simplified by an experiment which holds all but one of the reactants at a large concentration (therefore relatively constant) as in Expt 5.

SKILL: The integrated rate laws can be used to determine the rate law for a reaction if concentration and time data are provided. See Expt 5!

Once the form of the integrated rate law is known, then for any time, [A] is known, or vice versa.

So: another important piece of information can be deduced - the half life of a reaction. The half life is the time required for the reaction to be 50% completed or to have 50% remaining (glass half-full/half-empty). More next day...

Wednesday, November 30

Similar calculations can be used any time the extent of reaction is known: % reacted or complete or % remaining.

For my summary table, click here.

SKILL: calculate concentration or time based on the integrated rate laws.

Exercises: 28, 29, 30. Homework for Integrated Rates - for answers, click here

In general, for kinetics problems:

- pick equations carefully - concentration vs. what?
- if rate, then Differential
- if time, then Integrated
- use proper order: look for clues in the question
- given directly in words
- given in an equation
- given through the units of k

Use the Arrhenius equation to see how k depends on T.

SKILL: calculate activation energy from rate constants at different temperatures. Exercises: 34, 38, 40, 42 and a Homework problem, for answers, click here

What happens after the molecules collide? For the old exam question I used as an example, click here

For the reaction to occur, they will stick together in an activated complex :

- high energy (has its own potential energy called Transition State)
- short-lived
- maxima on the pathway curve

- can also react in a second step
- minima on the pathway curve